For cosmetic purposes, contact lenses having one or more colorants dispersed in the lens or printed on the lens are in high demand. These colored contact lenses enhance the natural beauty of the eye, or provide unique patterns on the iris of the wearer, or provide non cosmetic patterns or marks, such as rotation marks, inversion marks, product/brand codes, lot numbers, “DEMO” lenses, security mark and the like, which are of benefits to wearers, eye-care practitioners and manufacturers.
Various methods have been disclosed to make colored non-silicone hydrogel contact lenses (see, for example, disclosed in U.S. Pat. Nos. 4,668,240, 4,857,072, 5,272,010, and 5,414,477 and U.S. Patent Application publication Nos. 2003/0054109 and 2004/0044099, all of which are incorporated herein by reference). Commercially available colored contact lenses are prepared from non-silicone hydrogel material, such as, for example, a hydroxyethylmethacrylate (HEMA)-based hydrogel (i.e., a copolymer of HEMA with other comonomers and/or crosslinkers). Those non-silicone hydrogel lenses generally do not have high oxygen permeability. It is known that contact lenses must allow oxygen from the surrounding air (i.e., oxygen) to reach the cornea because the cornea does not receive oxygen from the blood supply like other tissue. If sufficient oxygen does not reach the cornea, corneal swelling occurs. Extended periods of oxygen deprivation cause the undesirable growth of blood vessels into the cornea. Hydrogel contact lenses conform closely to the shape of the eye, so oxygen cannot easily circumvent the lens. Thus, hydrogel contact lenses must allow oxygen to diffuse through the lens to reach the cornea, namely having relatively high oxygen transmissibility (i.e., oxygen permeability over the lens thickness) from the outer surface to the inner surface to allow sufficient oxygen permeate through the lens to the cornea and to have minimal adverse effects on corneal health. In addition, ion permeability is critical for healthy contact lens wear for silicone hydrogel contact lenses since the tear layer on both sides of the lens behavior as a dilute salt solution. Lenses with appropriate levels of ion permeability are generally characterized as being required for acceptable clinical performance, such as for example on eye movement, which is especially important in the case of silicone hydrogels.
In recent years, silicone hydrogel contact lenses, for example, Focus NIGHT & DAY™ (CIBA VISION), become more and more popular because of corneal health benefits provided by their high oxygen permeability and comfort. However, few methods have been developed for making colored silicone hydrogels contact lenses, in particular, which has good quality of the finished lens' printed pattern.
Therefore, there are needs for a method for making colored silicone hydrogel contact lenses with high ion permeability, high oxygen permeability and a high-quality color image.